This invention relates to improved climbing devices used for assisting rock climbers in anchoring their climbing ropes at cracks or crevices in rock faces.
Prior art climbing devices of the type described in Jardine U.S. Pat. No. 4,184,657 and Lowe U.S. Pat. No. 4,645,149 incorporate multiple spring biased cams which can be wedged between the opposite walls of a crack or crevice in a rock structure being climbed. The cams are biased to an open position corresponding generally to the maximum spacing between the opposed walls and can be manually retracted to a closed position for convenient insertion into the crack. Upon release of the manual retracting force the cams move toward the open position until they engage the opposite walls. A tug or pull on the climbing device after engagement with the walls causes the cams to tightly wedge against the walls because of the changing radii of the surfaces of the cams which engage the crack walls. The Jardine device, commonly known as the "Friend" climbing device has a sturdy rigid support bar on which all of the components are carried. The end of this bar remote from the cams has an aperture for attachment of a climbing rope. During use of this device it has been well recognized that shifting forces on the rigid support bar cause it and the cams to change position in the crack resulting in a "walk" of the cams to a deeper position in the crack, sometimes to a position where it is difficult or impossible to manipulate the operating bar to release the cams when removal of the device is attempted. Some climbers have even found it necessary to attach an extra cord or other extension to the operating bar to be able to actuate the cams for release when they have progressed too far into the crack.
A climber using a Jardine type of device must often choose between one placement which allows relatively easy access to and manipulation of the operating bar for insertion and removal of the device and another in which the supporting bar does not protrude significantly beyond the rock face. In such a device with a rigid support bar, if the end of the bar to which a rope is attached protrudes beyond the rock face, the force of a fall by the climber may apply a bending force to the bar sufficient to cause the bar to break, thereby rendering the device ineffective as an anchor to protect against such a fall. This problem becomes more acute as the size of the device and the corresponding size of the support bar are decreased.
The device of FIGS. 1 through 4 of the Lowe patent is generally similar to that of Jardine as far as the "walking" problem is concerned. The other embodiments of Lowe in FIGS. 5 through 16 have the cams supported between the ends of a rigid bifurcated member. The other end of this member has extending therefrom a single rod or cable which has a rope receiving loop spaced from the end of the cam supporting member. The rod or cable supports a cam actuator which in its released position abuts the end of the rigid bifurcated member. The cam actuator is directly connected to the cams by small cables and is directly engaged by the fingers of the climber to manually pull it away from the bifurcated member to withdraw the cams against their biasing springs to their retracted positions to allow insertion of the device into a crack. These other embodiments do not provide any significant flexible portion of the device along their axial length between the cams and the manually-engaged cam actuator. Thus the same "walking" problem exists.
The use of a cable for a portion of the support member as described in an alternative embodiment of Lowe may partially overcome the problem of breakage of the Jardine device as described above but does not allow ready access to the cam actuator should the device be inserted or "walk" deeply into a crack.
Other climbing devices which are adjustable and which utilize flexible support cables but which do not utilize camming heads include those described in Guthrie U.S. Pat. No. 4,643,378 and Phillips U.S. Pat. No. 4,572,464. Guthrie and Phillips each disclose embodiments in which the actuating member provides some distance between the operating head and the means of operation by the climber but do not offer the advantage of the present invention. In neither case is a coaxial relationship of support cable and actuating means disclosed. In each case these two elements are side by side. By having separate axes for these two elements the operation of either device depends on the stiffness of the cables to overcome the bending force which results from the application of tension on one element and compression on the other as is necessary for the operation of each device. Furthermore both Guthrie and Phillips have operating heads which are comprised of two relatively movable members and are not symmetrical about the main axis of the device as is the present invention. Even disregarding the inherent disadvantages of actuating means as described in Phillips and Guthrie, neither would lend itself to use in the present invention in which effective operation of the camming head requires application of a force parallel to the main axis of the device to each of the several camming members which are essentially symmetrical about the main axis of the device but which are spaced at varying distances from the axis.
Climbing anchors in use can be subject to significant abrasion by being in contact with the rock surface being climbed and the jostling movement caused by a climbing rope passing through a carabiner attached to the anchor as a climber proceeds up a rock face. An example of a common situation which might tend to cause this sort of abrasion is shown in FIG. 2 in which portions of the present anchoring device are shown hanging over a rock edge. Over time, this abrasive action can cause enough wear to any piece of climbing equipment so as to make it incapable of supporting any significant load, particularly the high load to which it can be subjected when a climber falls while relying on it for protection. The failure of such a device under these circumstances can result in otherwise avoidable serious injury to a climber.